Windows PowerShell 3.0 detects unexpected losses of connectivity between the client and server and attempts to reestablish connectivity and resume execution automatically.
If the client-server connection cannot be reestablished in the allotted time, the user is notified and the session is disconnected. During the attempt to reconnect, Windows PowerShell provides continuous feedback to the user.

If the disconnected session was started by using the InvokeCommand, Windows PowerShell creates a job for the disconnected session to make it easier to reconnect and resume execution.

These features provide a more reliable and recoverable remoting experience and allow users to perform long-running tasks that require robust sessions, such as workflows.

Enhanced Online Help. Use the following command to open the online help document of a cmdlet.

Windows PowerShell 3.0 include support for the Common Information Model (CIM), which provides common definitions of management information for systems, networks, applications and services, allowing them the exchange of management information between heterogeneous systems. Support for CIM in Windows PowerShell 3.0, including the ability to author Windows PowerShell cmdlets based on new or existing CIM classes, commands based on cmdlet definition XML files, support for CIM .NET Framework. API, CIM management cmdlets and WMI 2.0 providers.

Improvements to Modules. This is mostly a quality-of-life improvement for PowerShell module developers.

PowerShell ISE

The input and output panes have been merged to better resemble the actual shell.

Intellisense has now come to PowerShell ISE!

This is tab-completion on steroids. As you type, ISE recognises partially typed cmdlet names, cmdlet parameter names, enums, etc, and offers possibly alternatives. If you type, say Get- and pause, PowerShell ISE brings up a set of useful items beginning with 'Get-;, such as Get-AsciiEncoding, etc. This provides a huge benefit for those writing scripts - not only will PowerShell cut down on the typing, but things such as parameter names now get spelled out in full (a good thing for production scripting).

Command Add-on - you can now browse commands in a graphical way. If you select a command you can enter parameters and run the command. This can also be accessed any time with Show-Command.

Workflows

Workflows are a new type of PowerShell script. They're most useful in large-scale automation tasks.

A workflow is a sequence of programmed, connected steps that perform long-running tasks or require the coordination of multiple steps across multiple devices or managed nodes. Windows PowerShell Workflow lets IT pros and developers author sequences of multi-device management activities, or single tasks within a workflow, as workflows. By design, workflows can be long-running, repeatable, frequent, parallelizable, interruptible, stoppable, and restartable. They can be suspended and resumed; they can also continue after an unexpected interruption, such as a network outage or computer restart.